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The Pi limits output power to USB devices to 140mA. The reading on TP1 and TP2 will not constant - the Pi does a lot of on-board power management. The dongle will draw more when transmitting. The SD card will draw more when writing. If you run a GUI, the GPU will be powered up, etc.

Try running with wired ethernet and no wifi dongle. See if your power woes go away. I suspect they will.

Bottom line: you're going to have to use a powered hub for the dongle. I've offered this same solution to several customers over the last month or so and it's worked for them. I've had to do it myself.

Not broken. It's just that they're running very close to the edge on their power budgets. That's why they need the power management.

And it really is a good idea to check all of your peripherals against the Verified Peripherals list. It's not just Wifi that's a problem - they identify quite a few keyboards and mice which draw too much juice.

This Wifi issue seems to have ballooned on us over the last few weeks. We've updated our product pages and tutorials to recommend connecting WiFi dongles only through powered hubs.